are you forced to use schottky diodes as the detector (since they do not work at the lowest level of -35 dBm)? You would probably need TWO diodes at each port, one with a 10 dB amplifier in front of it, and combine their outputs in an analog op amp linearizer.
IF you can use one of the IC power detectors from Linear Technology or Analog Devices, it will be much easier. Instead of simple diodes, they use LogAmplifier circuits to detect the RF power over a very wide dynamic range.
Remember...you are getting a VERY small DC voltage at the diode output for -35 dBm, and it will be masked by general noise...so it will be hard to find the true signal.
Also, if you are using just schottky diodes....you need to realize that they have a DC bias point drift and gain drift as a function of temperature, and you need to compensate for both
also, consider your ADC. You have an ADC with a 0 to 3 volt input range, and are only putting in 3 to 71 mV? You are not going to get a very good bit sensitivity doing that!